Air conditioner filter indicator



' Jan. 25, 1955 J. CALLING ,7

AIR CONDITZEONER FILTER INDICATOR Filed Nov. 1, 195.2

PC, IQ I 5 5? United States Patent C AIR CONDITIONER FILTER INDICATOR John Calling, Evansville, Ind., assignor to International Harvester Company, a corporation of New Jersey Application November 1, 1952, Serial No. 318,305

4 Claims. (Cl. 116-117) This invention relates generally to air conditioner controls and more specifically to improvements in indicators for indicating the cleanliness condition of air conditioner air filters.

It is an object of this invention to provide an indicator in an air conditioner having an air filter disposed within an intake or exhaust duct for indicating the cleanliness condition of the air filter.

It is a further object of this invention to provide a simple, eflicient and positive indicator for visually indigitting the cleanliness condition of an air conditioner air ter.

A feature of this invention is a very flexible diaphragm, exposed to the airbetween an air filter and a fan assembly of an air conditioner, which will assume a shape, relative to a normal shape, dependent upon the cleanliness condition of the air filter.

Other objects and features of the instant invention will be apparent upon a perusal of the following specification and drawing of which:

Figure l is a partial crosssectiona1 top view of one embodiment of the instant invention;

Figure 2 is a partial cross-sectional top view of another embodiment of the instant invention; and

Figure 3 is a partial end view of the indicator means viewed along the line 33 of Figure 1.

The present embodiments are the preferred embodiments but it is to be understood that changes can be made in the present embodiments by one skilled in the art without departing from the spirit and scope of the instant invention.

For a detailed description of the invention, reference is made to Figures 1 and 2 wherein two embodiments of the invention are shown. The invention is shown as applied to part of an air conditioning system. Referring to Figure 1, a casing 3 is shown. An intake duct 4 is mounted to one side of the casing 3 and an exhaust duct 5 is mounted to another portion of the casing 3. Interconnecting the intake duct 4 and the exhaust duct 5 is a fan chamber 27. A fan 9 operated by a motor 8 is positioned within the fan chamber 27 so as to draw air into the intake duct 4 and to force it from the exhaust duct 5. An air filter 6 and an evaporator 26 are mounted within the intake duct 4. The filter indicator mechanism is mounted within the fan chamber 27, and one side thereof communicates with the air outside of the casing 3 through the opening 12. Now, as can easily be seen in Figure 1, the motor 8 operates the fan 9 to draw air into the intake duct 4, through the filter 6, through the evaporator 26, through the fan chamber 27 and to force that air out of the exhaust duct 5.

seen in Figures 1 and 2, the air filter 6 is removably mounted within the channels 7 disposed along the inner walls of the intake duct 4 and the exhaust duct 5 respectively. As the air filter becomes clogged with dirt, it olfers a substantially high resistance to air flow therethrough. This high resistance will decrease the efficiency of the air conditioner, and it is therefore important that means be provided for easily indicating when the air filter is dirty. Such means is the mechanism 10 which is described in detail below.

It can be seen from Figure 1 that as the air filter 6 becomes clogged with dirt and ofiers a progressively higher resistance to the air drawn therethrough, a partial vacuum will be produced within the fan chamber 27 in relation to the air outside of the casing 3. Furthermore, it can be seen from Figure 2 that as the air filter 6 becomes clogged with dirt and offers a progressively higher resistance to the air passing therethrough, a pressure greater than the air pressure outside of the casing 3 will be produced within the fan chamber 27. The mechanism 10 utilizes these different air pressures to indicate the cleanliness condition of the air filter 6.

The mechanism 10 as shown in Figures 1 and 2 comprises a casing 28 mounted to one wall of the casing 3. Across the opening in the casing 28 a diaphragm 11 is securely mounted at its edges 18 by any well known mounting means. The diaphragm 11 is constructed of a very flexible rubberized fabric or any other material of a similar resiliency. To the center of the diaphragm 11 The embodiment shown in Figure 2 is similar to that of Figure 1 and similar parts have been designated with the same numerals used in Figure 1. As seen in Figure 2, the air filter 6 is mounted within the exhaust duct 5 and the fan 9 and motor 8 are mounted within the fan chamber 27xin cooperation with the intake duct 4. The motor 8 then operates to operate the fan 9 which in turn causes air to be drawn into the intake duct 4, through the evaporator 26, and to force that air through the fan chamber 27, through the air filter 6 and out of the exhaust duct 5.

The air filter 6, as is well known in the art, is fabricated from a material that will allow a free passage of air therethrough, while effectively removing and retaining dust and dirt particles from the air moving therethrough. The air filter 6 is replaceable when dirty, and as can be an element 14 is.securely mounted by means of mounting means 17. A bell crank 13 is provided which is pivotally mounted by means of mounting means 16 to the casing 28. One arm of the bell crank 13 is pivotally mounted to the end of the element 14 by means of mounting means 15. On the other arm of the bell crank 13 an indicator scale 21 is mounted. The indicator scale 21 is formed in the shape of an arcuate strip. Identifying marks or symbols 22, 23 and 24 are placed upon the indicator 29 to provide a visual indication of the cleanliness condition of the air filter 6. These identifying marks or symbols 22, 23 and 24 can be printed words such'as clean, half dirty and dirty, or paints of different colors, such that different colors will indicate difierent conditions of cleanliness of the air filter 6. The opening 12 in the casing 3 is also within the casing 28 and serves a dual function. First, the opening 12 permits air to move between the casing 28 and the air outside of the casing 3. Second, the opening 12 as can be seen in Figure 3 serves as a window for a visual reading of the condition of the air filter 6. As the identifying marks 22, 23 and 24 pass before the opening 12, the cleanliness condition of the air filter may be easily seen by anyone maintaining the air conditioning unit. It should be noted that the identifying marks or symbols 22, 23 and 24 of Figure 2 are mounted upon the indicator scale 21 in a reverse order from the mounting of these marks in Figure 1-.

To properly bias the diaphragm 11, or to calibrate the mechanism 10 so that the correct condition of the air filter 6 may be read through the opening 12, biasing spring 19 is provided. As can be seen in Figures 1 and 2, one end of the biasing spring 19 is mounted to the arm of the bell crank 13 having the indicator 21 thereon. The other end of the biasing spring 19 is attached to a screw which partially projects through the casing 28. A nut 20 is threaded upon this screw. The biasing spring 19 of Figure 1 serves to bias the bell crank 13 in a clockwise direction as viewed in Figure 1, and thereby provides means for properly calibrating the mechanism 10. The biasing spring 19 of Figure 2 serves to bias the bell crank 13 in a counterclockwise direction as viewed in Figure 2.

To describe the detailed operation of the various embodiments of the invention, reference is first made to Figure 1. When the air filter 6 is clean a minimum resistance will be offered to air passing therethrough and, consequently, the air pressure in the fan chamber 27 will approximate the air pressure outside of the casing 3. Thus the diaphragm 11 will assume its normal position. This normal position is determined by the biasing spring 19 and, as can easily be seen, the diaphragm 11 will assume a position of maximum distortion. In

other words, the bell crank 13 will assume the maximum clockwise position as viewed in Figure 1, and the identifying mark 22 will be positioned before the opening 12 to indicate a clean air filter. Now, as the air filter 6 becomes progressively clogged with dirt, and. as the, fan 9 operates; at a constant. rate, the air filter 6 will otter a progressively increasingresistance to air pass ing therethrough, and. a progressively increasing partial vacuum will be created between the air filter 6 and the fan 9. In other words, the air pressure acting against the diaphragm 11 Within the fan chamber 27 will become progressively less than the air pressure caused by air communicating with the diaphragm 11 through the opening 12. This will cause the. diaphragm 11 to assume positions of lesser and lesser distortion, and the diaphragm 11 will pivot. the bell crank 13 in a counterclockwise direction aga nst. the bias of the spring 19 as viewed in Figure 1. As, thebell crank 13 pivots further and further in a counterclockwise direction, the identifying mark 23 will be moved to a position before the opening 12. to indicate a partially dirty air filter, and when the air filter is substantially completely clogged and in condition for replacement, a maximum resistance. will be offered by the air filter 6 to air passing therethrough, and the identifying mark 24 will. be poigitioned before the opening 12 to indicate a dirty air ter.

To discuss the detailed operation of the embodiment of the invention shown in Figure 2, reference is made thereto. When the air filter 6 is clean a minimum resistance will be ofiered to air passing therethrough and the air pressure in the fan chamber 27 will approximate the air pressure outside of the casing 3. The spring 19 will then pivot the bell crank 13 to its maximum counterclockwise direction as viewed in Figure 2 and the diaphragm 11 will then assume a position of maximum distortion. The identifying mark 22 will be positioned before the opening 12 to indicate a clean filter. When the air filter 6 is approximately half clogged or dirty, the air pressure in the fan chamber 27 will be. increased from the normal by a proportional amount. This increase of air pressure in the fan chamber 27 over the air pressure of the air outside of the casing 3, which as noted above iscommunicative to the casing 28, will cause the diaphragm 11. to assume a position of a smaller distortion. Thev diaphragm 11 will then cause the bell crank 13 to be pivoted in a clockwise direction as viewed in Figure 2 against the tension of the biasing spring 19 to a position wherein the identifying mark 23 will be be.-

fore the opening 12. Thus anyone maintaining the air conditioning unit may easily see. that the. air filter 6 is half clogged or dirty. When the air filter 6- is effectively completely clogged, a maximum resistance will be oiiered to air passing therethrough and this will cause a maximum air pressure within the fan chamber 27 in comparison'to the outside. air pressure. This incremental increase ofair pressure exerted against the diaphragm 11 will cause the diaphragm. 11 to assume a position of minimum distortion, and the diaphragm 11 will. in turn pivot the bell crank 13 in a clockwise direction, as viewed in Figure 2, to a position of maximum rotation. Thus the identifying mark 24 will be positioned before the opening 1.2 to indicate a dirty air filter.

Having described the invention, what is considered new and desired to be protected by Letters Patent is:

1. In an air conditioning system having a duct system, having an air filter removably mounted across said duct'system, and having means for drawing air through said duct system and through said, air filter, said air filter uttering a slight resistance to said air passing therethrough when clean, and a substantial resistance thereto when dirty, the means for indicating the cleanliness condition of said air filter comprising a flexible diaphragm mounted to be exposed one side thereof to said air passing through said duct system and on the other side thereof to air without said duct system whereby said air passing through said duct system projects against said diaphragm with a force proportional to the resistance offered by said air filter, a bell crank pivotally mounted in said air conditioning system, an element secured to the center of said diaphragm and pivotally mounted to one arm of said bell crank, a biasing spring mounted in said air conditioning system and attached to the other armuof said ball crank-torotatively bias said bell crank in the. opposite direction to the direction of rotation produced by said air passing through said duct system and projecting against said diaphragm, an indicator element mounted on said other arm of said bell crank for indicating the cleanliness condition of said air filter.

2. In an air conditioning system having a duct system with an air filter disposed thereacross wherein said air filter offers a slight resistance to air passing through said duct system when said air filter is clean, and a substantial resistance to said air passing through said duct system when said air filter is dirty, means for indicating the resistance of said air filter to said air passing through said duct system comprising a flexible diaphragm disposed Within said duct system in a parallel air flow relationship with said air filter whereby said flexible diaphragm is distorted by said air passing through said duct system an amount proportional to the amount of dirt in said air filter, an element mounted at the center of said diaphragm whereby said element is movable as. said flexible diaphragm is distorted, a. bell crank pivotally mounted in. said air conditioning system, pivotal mounting means interconnecting said element and one arm of said bell crank, a biasing spring, one end. of said biasing spring adjustably secured in said air condition- I ing system, the. other end .of said biasing spring attached tov the. other arm of. said bell. crank, whereby said bell crank is biased by said biasing spring. in a direction opposed. to the direction. said bell crank is moved when said diaphragm is distorted, registering. means mounted on theend of said other arm. of said bell crank for indicating the extent of distortion of said diaphragm, whereby the cleanliness. condition of said air filter is registered.

3. An. air conditioning system having. a duct system with an air filter disposed vthereacross wherein said air filter offers a slight resistance to. air passing through said duct system when. said air filter is. clean, and a substantial resistance to said air passing through said duct sys tem when said air filter is dirty,.means for indicating the. resistance of said air; filter to said air passing through said duct system comprising a flexible diaphragm mounted within said duct system in: a. parallel air flow relationship with said air filter whereby. said flexible diaphragm is flexed by said. air passing. through said duct system an amount proportional. to. the amount of. dirt in said air filter,.an element mounted at the center of said diaphragm whereby said element is. movable as said diaphragm is flexed, a. bellcrank pivotally mounted in said air conditioning system, pivotal mounting means interconnecting said element and one arm of said bellcrank, a coiled spring,.one-end of said coiled springsecured to a screw, said screw adiustably secured in said air conditioning system, the. other .end of saidcoiled spring attached to the other arm of, said bellcrank intermediate the ends thereof to' pivot said bellcrank to adjustably bias said diaphragm to a position. of maximumdistortion when said air filter is clean and to a position of minimum distortion when said, air filter is dirty, registering means mounted on the end. of. said other arm of said bellcrank for indicating the. extent of distortion ofsaid diaphragm, whereby the cleanliness condition of. said air filter is registered.

4. In. an air conditioning: system having a duct system with an air filter disposed thereacrosswherein said air filter offers aslight resistance to air passingthrough said duct system whensaid air filter is clean, and a substantial' resistance to. said air passingthrough said duct system when said air filter is dirty, means for indicating. the resistance of said air filter to said. air passing through said duct system comprising a flexible diaphragm mounted within said duct system-in aparallel air flow relationship with said air filter whereby'said flexible diaphragm is flexed by; said air passing through said duct system an: amount proportional to-the amount of dirt in said air filter, an element mounted at the center of said diaphragm-whereby said element is movable as said diaphragm is flexed; a bellcrank pivotally mounted in said air-conditioning system, pivotal mounting means interconnecting said element and one arm of said bellcrank, a coiled spring, one end of said coiled spring secured to a screw adjustably secured in said air conditioning system, the other ofsaid' coiled spring attached to the other arm'of said bellcrank intermediate the ends thereof topivot said bellcrank to' adjustably bias said diaphragm 'to a position of minimum distortion when said air filter is. clean and toe position of maximum References Cited in the file of this patent UNITED STATES PATENTS Bilde Mar. 17, 1936 Gerber Nov. 16, 1937 Mueller Sept. 12, 1939 Snyder Apr. 30, 1940 Nystul Sept. 26, 1950 

